It’s been pretty difficult lately to find a good mainstream science fiction film.

At least one that is an actual science fiction film. There’s lots of movies that feature science fiction, of course – as a theme!

Of course blockbuster and franchise science fiction, from Aliens to Star Trek to Terminator are as much about spectacle as they are about anything. Other films, while seemingly sci-fi on first glance, appear afraid to alienate mainstream audiences with all that nerdy crap, and quickly ditch out to action or horror elements. But possibly the most frustrating offenders are films that pose as science fiction so convincingly for the first two acts, then chicken out at the last minute by wedging in (and being overtaken by) an awkward spiritual message, love story or religious overtone (Lookin’ at you Arrival! You too, Interstellar!).

Annihilation, to its own credit, largely sidesteps those issues. It is a rare, unapologetic science fiction movie.

Loosely adapted from the book of the same name, Annihilation introduces us to Lena, a professor of cellular biology, and a military veteran and spouse who is attempting to move on a year after her husband’s (Oscar Isaac) disappearance during a special operations mission.

A shocking encounter puts Lena face to face with the very organization that sent her husband out in the first place. At a base outside a mysterious and growing quarantined zone known as the “Shimmer” Lena learns that nothing – almost nothing – that goes into the Shimmer ever returns. Seeking answers for herself and on behalf of her husband, she volunteers her convenient expertise on the next mission.

We get to the Shimmer quickly, and while they’re convenient, Lena’s “particular set of skills” are delivered realistically enough to take at face value. The rest of the party, all also women, make up a familiar movie roll-call of skillsets: Dr. Ventress (Jennifer Jason Leigh) , a psychologist and the leader of the group; Anya Thorensen (Gina Rodriguez), a paramedic; Josie Radek (Tessa Thompson), a physicist; and Cass Sheppard (Tuva Novotny), a surveyor.

The film actively refuses to make a big deal out of the fact that the team is made up of all women, even eschewing the book’s explanation, again to its own service, making it quietly clear that should this be the kind of thing that concerns you, the movie will be proceeding regardless.

We discover that this bubbled ecosystem, in addition to blocking out surveillance and communications, is altering life fundamentally, turning both plants and animals into strange, sometimes beautiful, sometimes dangerous versions of themselves. The shimmer only grows stranger the closer the team moves to the center. As the mystery and darkness of the Shimmer is pulled back, a series of flashbacks do the same for how we understand Lena and her husband Kane as well. Seeing what drives her forward to unravel the Shimmer’s mystery and what sent Kane there to begin with become necessary the further we go. Lena begins the movie as kind of a mystery, but the more we learn, the more we understand her nature, her drive, and even a kind of ruthlessness she possesses. She is driven by scientific curiosity and personal motivation to get to the end of this. And when she does, the movie doesn’t disappoint.

And that very fact is one of three important areas that make Annihilation a good science fiction film.

The humanity.

Each character in Annihilation is nuanced enough to have some surprise to them, with the possible exception of Gina Rodriguez’ Anya, a kind of bafflingly stereotypical aggressive lesbian Latina trope. Thankfully even she gets some surprising moments — just not enough of them. Jennifer Jason Leigh’s team leader shrewdly and frustratingly keeps her crew at arm’s length throughout the film in ways that heighten the story. Thompson’s Josie seems most to illustrate one of the biggest themes of the film: None of these women, knowing the fate of previous expeditions, expect or even necessarily want to return from the Shimmer. As shocking, weird and frightening the threats of the shimmer are, the underlying feeling is pain, not horror. It’s pain that the team members bring with them, and the way that the Shimmer enhances their pain in almost tailored ways.

Meanwhile, through Portman’s excellent expressions, Lena’s reactions mirror our own. The curiosity, the confusion, the drive to get to the end and quite often the terror. Speaking of which …

The monsters.

There’s not a huge amount of monster moments. Cheap jump scares are almost nonexistent. But just as we get comfortable, the film finds the right moment to be jarring. The weirdness of the Shimmer could have been handled completely wrong. Director Alex Garland could have easily been tempted to cobble far more strange and imaginative monsters. But it’s the familiarity of the mutations, the wrongness of how they are changed that give the creatures their real power. The animals of the Shimmer run the gamut from exotic to disconcerting to NIGHTMARE FUEL! They feel less fanciful and more possible and that gives them power. The movie’s explanation for their terrifying nature grounds them. The science grounds them.

“don’t let go!”

The science.

Science fiction, too often, is just code for “movie magic.” Some of the best science fiction concepts, from The Island, to Minority Report to (ugh!) Passengers, flirt with originality and new ideas before utterly squandering it! Consistently, they surrender to quick and easy spectacle and watered-down science, taking the story along with it. Annihilation throughout largely succeeds in maintaining its science even at the expense of more excitement.

Though the researchers and explorers in Annihilation are unsure of the origin of the Shimmer, they are desperate to understand and counter the phenomenon that they learn is mixing of genetic code and instructions (I refrain from the word “splicing,” as poor science fiction shortcut storytelling has made the word all but meaningless). You see them trying to understand it, maybe even more so than trying to prevent it from spreading – if they even can. The powerlessness of that prevents Annihilation from being another Aliens clone. There’s a realism and possibility to what the Shimmer is doing to its ecosystem. The way it affects the world in frightening ways, yes. But also in how much of what it does is mundane or benign. The cause of this biological reprogramming is presented realistically enough at least, without leaning on unobtanium so heavily that one could dismiss the whole thing with a 9th grade Bio textbook.

In the end we get just enough answers to satisfy, and just enough mystery to leave us wondering about the world, the possibility of what else could be out there. And also just enough maybe to want a sequel?